The present invention relates to a monitor and alarm system for a central refrigeration installation for refrigerated display cases.
In commercial refrigeration installations for supermarkets where a number of refrigerated display cases are employed, typically a plurality of refrigerant compressors are utilized to supply high pressure liquid refrigerant to the evaporators contained in the display cases. Typically, a bank of such compressors will be coupled in parallel between a common input refrigerant manifold and an output manifold which, in turn, is coupled to a receiver containing a mechanical refrigerant liquid level sensor. The evaporators of each refrigerated display case are then commonly coupled to the refrigerant receiver and the outputs of the evaporators return to input manifold completing the refrigerant flow path. Certain refrigeration installations also incorporate a heat reclaiming system, which is used for ancillary heating functions such as room temperature control or heating water. Typically these heat reclaiming systems include a heat exchanger coupled in series to the refrigerant flow path, so that the warmed refrigerant can be selectively diverted or shunted by a valve or valves through the heat reclaiming system as required.
In the past, a mechanical dial-type refrigerant level float was mounted to the receiver to provide a local visual indication of the liquid level. Also, a separate fixed alarm switch, set for approximately 20% of liquid level, was provided to provide an alarm output signal at the fixed level for activating a suitable alarm to the system operator. Systems also typically include oil failure sensing switches at each compressor for detecting the oil level or oil pressure PM in each compressor and a remote panel indicating oil level or pressure PM failures as well as monitoring other functions such as suction and discharge pressures at the input and output manifolds, respectively, and a voltage sensor to detect the loss of any one of the three phase input power employed for powering the compressors.
Thus, although some form of monitoring was provided for some conditions in such a system, the known prior art does not provide an integrated monitoring and alarm system whereby a central panel is provided to display all of the monitored fault functions as well as provide, in addition to the alarm indications, a display of the actual refrigerant level.
Another problem is associated with refrigeration installations incorporating heat reclaiming systems. When the heat reclaim is in operation and refrigerant is diverted therethrough, the level of refrigerant within the remainder of the refrigeration system drops significantly. Thus, the engagement of the heat reclaim system at times when the refrigerant level is already low exacerbates the already undesirable low refrigerant level condition.